Preheat oven to 350 degrees. Butter a 13-by-9-inch glass baking dish. Place the cream cheese milk and butter in a saucepan and cook, stirring, over low heat until the cheese has melted. Place mashed potatoes in a large bowl and stir in cheese mixture. Add the jalapenos, corn salt and pepper. Mix well and soon into the baking dish. Bake about 30 minutes.